In fact, this is not quite what I wanted. I should have written
def factor(self, *args, **kwds)
return self.numerator().factor(*args, **kwds) / \
self.denominator().factor(*args, **kwds)
In the meantime, while waiting for further comments, I've put this up
as ticket #7868. I'll test this now and, if nothing fails, upload the
patch later today.
Sebastian
On Jan 7, 4:50 pm, John Cremona <[email protected]> wrote:
> 2010/1/7 Sebastian Pancratz <[email protected]>:
>
>
>
> > Further to my earlier post, a search for "def factor(self," in the
> > Sage library reveals that there are a lot of instances where the
> > factoring method supports various arguments. Thus, at the very least,
> > I think the fraction field implementation should allow further
> > arguments, too, and simply forward them, that is, the code should
> > change from
>
> > def factor(self):
> > return self.numerator().factor()/self.denominator().factor()
>
> > to
>
> > def factor(self, *args)
> > return self.numerator().factor(args)/self.denominator().factor
> > (args)
>
> That looks like a good, simple solution. Can anyone see any
> drawbacks? If not, it would be a simple patch (but requiring full
> testing!)
>
> John
>
> > Moreover, I guess the parameter "proof" should be documented in the
> > method "factor" for multivariate polynomials.
>
> > Sebastian
>
> > On Jan 7, 4:11 pm, Sebastian Pancratz <[email protected]> wrote:
> >> Dear John,
>
> >> I haven't written any of the code involved, so I am not absolutely
> >> sure about this, but after looking at the code for a few minutes, I
> >> think the following is the case:
>
> >> The "FractionFieldElement" objects have a method "factor", but this
> >> takes no arguments other than "self". This explains the error message
> >> in the second case you describe. On the other hand, the
> >> "MPolynomial_libsingular" objects provide the method "factor(self,
> >> proof=True)". Here, however, the parameter "proof" is only used to
> >> prevent certain inputs (with the option "proof=True" set) from being
> >> passed to Singular, presumably(?) in cases when Singular's results
> >> might not be reliable. There appears to be no further use of the
> >> parameter.
>
> >> I think this is something that ought to fixed. (N.B. I don't think I
> >> know enough about what kind of factoring methods rings in Sage
> >> typically offer.) If rings often offer further arguments to the
> >> method "factor", then I think the method "factor" for
> >> FractionFieldElement objects should be modified to allow the same
> >> arguments. On the other hand, if "MPolynomial_libsingular" is the
> >> only case where "factor" takes further arguments, perhaps the second
> >> argument ought to be removed?
>
> >> Sebastian
>
> >> On Jan 7, 3:32 pm, John Cremona <[email protected]> wrote:
>
> >> > I define a rational function in two variables over a finite field:
>
> >> > {{{
> >> > sage: R.<x,y> = GF(2)[]
> >> > sage: f = x*y/(x+y)
> >> > sage: f.parent()
> >> > Fraction Field of Multivariate Polynomial Ring in x, y over Finite
> >> > Field of size 2
>
> >> > }}}
>
> >> > I try to factor it, and get this error:
>
> >> > {{{
> >> > sage: f.factor()
> >> > ---------------------------------------------------------------------------
> >> > NotImplementedError Traceback (most recent call
> >> > last)
>
> >> > /home/masgaj/.sage/temp/host_56_150/17587/_home_masgaj__sage_init_sage_0.py
> >> > in <module>()
>
> >> > /local/jec/sage-4.3.rc0/local/lib/python2.6/site-packages/sage/rings/fraction_field_element.so
> >> > in sage.rings.fraction_field_element.FractionFieldElement.factor
> >> > (sage/rings/fraction_field_element.c:2972)()
>
> >> > /local/jec/sage-4.3.rc0/local/lib/python2.6/site-packages/sage/rings/polynomial/multi_polynomial_libsingular.so
> >> > in
> >> > sage.rings.polynomial.multi_polynomial_libsingular.MPolynomial_libsingular.factor
> >> > (sage/rings/polynomial/multi_polynomial_libsingular.cpp:22701)()
>
> >> > NotImplementedError: proof = True factorization not implemented. Call
> >> > factor with proof=False.
>
> >> > }}}
>
> >> > So I do what I am told, but:
>
> >> > {{{
> >> > sage: f.factor(proof=False)
> >> > ---------------------------------------------------------------------------
> >> > TypeError Traceback (most recent call
> >> > last)
>
> >> > /home/masgaj/.sage/temp/host_56_150/17587/_home_masgaj__sage_init_sage_0.py
> >> > in <module>()
>
> >> > TypeError: factor() takes no keyword arguments
>
> >> > }}}
>
> >> > Worth a ticket, I think?
>
> >> > Also, does anyone know what the proof parameter for this sort of
> >> > factorization actually means?
>
> >> > John
>
> > --
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>
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